Radiant drying of particulate material



May 17, 1966 c. E. ALLEMAN RADIANT DRYING OF PARTICULATE MATERIAL 2 Sheets-Sheet 1 Filed April 9, 1962 INVENTOR. C.E. ALLEMAN A TTORNE Y5 May 17, 1966 c. E. ALLEMAN RADIANT DRYING OF PARTICULATE MATERIAL 2 Sheets-Sheet 2 Filed April 9, 1962 INVENTOR. C.E. AL LEMAN United States Patent 3,251,137 RADIANT DRYING 0F PARTICULATE MATERIAL Carl E. Alleman, Bartlesville, 0kla., assignor to Phillips Petroleum Company, a corporation of Delaware Filed Apr. 9, 1962, Ser. No. 186,146 Claims. (Cl. 3431) This invention relates to the removal of volatile liquid from particulate material. In one aspect the invention relates to process and apparatus for drying wet pelleted carbon black. In another aspect this invention relates to a rotary drum dryer and to a method of operation of the dryer. In another aspect this invention relates to treating carbon black at elevated temperatures.

In some chemical processes the resulting product is in the form of small solid pellets which, however, have some residual moisture content which must be lowered. An example of such a product is ammonium nitrate fertilizer which is produced in the form of prills which require an additional drying step following the formation of the prills. In other processes the product is formed in pellets which consist of very finely divided particles gathered together to make the individual pellets, and in this type of process the formed pellet often contains a. relatively large amount of moisture which must be removed in a subsequent drying step. An example of this type of process is the production of carbon black utilizing a wet pelleting process in which the pellets have a moisture content of approximately 50 percent, which must be lowered to less than 1 percent in a subsequent drying step. It is important, of course, in such drying operations to make the most eflicient use of the source. of heat energy and the apparatus components utilized, to prevent wasting heating fuel, for example, used to avoid excessive equipment installation costs.

An object of my invention is to remove volatile liquid from particulate material.

Another object of my invention is to make efiicient use of heating fuel in a drying operation. Another object of my invention is to avoid excessive equipment installation costs for a drying operation. Another object of my invention is to provide an eflicient and effective process and apparatus for drying wet pelleted carbon black. Another object of my invention is to treat the carbon black at elevated temperature.

Other aspects, objects and the advantages of my in vention are apparent in the written description, the drawing and the claims.

According to my-invention, particulate material is dried by subjecting it to direct radiation from radiant burners and subsequently subjecting the material to indirect heat exchange with heat from additional burners. Preferably, the drying is accomplished in a rotary drum dryer, while the burners supplying direct radiation are positioned with in the drum, while the burners supplying the heat for indirect heat exchange with the particulate material are located adjacent the drum downstream of the internal burners.

vided by subjecting a particulate material to be dried to direct radiation from radiant burners and to indirect heat exchange with the hot products of combustion from the burners. Preferably the hot products of combustion are subjected to a separation step to remove suspended solid material prior to being circulated around the outside of the dryer.

Further, according to my invention, efficient control of a radiant drying operation is provided by controlling each of a plurality of radiant burners separately according to the temperature influenced by each burner. Preferably, the control of each burner is for a temperature corresponding with the desirable discharge temperature,

Also, according to my invention, eflicient drying is pro 3,25 1, 13 7 Patented May 17, 1966 thus bringing each controller into effective operation as g the rate of flow of material to be dried or the moisture content varies. Further according to my invention carbon black is chemically treated at elevated temperatures.

Further, according to my invention, there is provided efiicient control of a radiant drying operation by controlling each of a plurality of burners separately under the influence of a single controller responsive to the discharge temperature of the material being dried. This can be accomplished for example, by connecting the output signal of a controller set for the desired discharge temperature with a valve in a separate control line for each burner, each valve becoming effective to reduce the flow of combustible mixture to the corresponding burner at different output pressures from the controller. Preferably the control is accomplished by connecting the output of a single controller to separate valves in separate lines supplying combustible mixture to separate burners and by selecting the valves to be responsive to different output pressures. Efficient control also can be obtained by making all valves responsive to the same output pressure of the controller, thus causing all burners to respond at the same time. I

In the drawing:

FIGURE 1 is a schematic vertical cross'section of a rotary drum dryer utilizing radiant burners inside the drum and heating burners outside the drum at a downstream location.

FIGURE 2 is a schematic vertical cross section of a rotary dryer having internal radiant burners and means for circulating hot combustion gases around the outside of the rotary drum.

FIGURE 3 is a schematic diagram of a control system for a radiant dryer having internal radiant burners.

In the embodiment illustrated in FIGURE 1, rotary drum 11 is supported on rollers 12 and 13; one or more of these rollers is driven from a suitable source of power, as for example electric motor 14 which is shown as being operably connected with rollers 12. Through suitable speed controls for motor 14 or speed change mechanism such as a gear box, shiftable belt, or chain, the speed of drum 11 can be regulated. Where the rotary dryer is a part of .an established plant, of course, it may be sufiicient that the drum be driven at a constant rate of speed which has been determined to be advantageous for that particular application.

The material'to be dried is fed through inlet pipe 16 and proceeds toward the right, as arranged in FIGURE 1, under the influence of the rotation of drum 11 and the force of gravity tending to level out the bed and tending to move the particle generally to the right due to a slight tilting of the axis of drum 11 in that direction. The level of the bed is determined by a scoop 17 which dips into the bed at each rotation of drum 11 and discharges a portion of the particulate material as it passes over the top on the next revolution. .The discharged material flows outward from the dryer through a discharge pipe 18. At its inlet end, drum 11 is provided with a relatively small diameter neck 19 which is provided with a seal with stationary housing 21 to prevent loss of particulate material at this point. A similar stationary housing 22 is. provided at the discharge end and cooperates with neck 23 to seal this end of the drum. A horizontal pipe 24 is supported by housing 21 and housing 22 and extends throughout the length of drum 11. This pipe serves to support necessary internal equipment and, where necessary, to supply cooling air through the interior of the drum.

Radiant burners 26 and 27 are supported within drum 98 keeps pipe connection 97 normally closed.

Fuel gas is supplied to burner 26 through a pipe 32 and to burner 27 through pipe 33. The flow through pipe 32 is controlled by a motor valve 34 while flow through pipe 33 is controlled by a motor valve 35. In the embodiment illustrated in this figure, an average temperature of the bed within the drum is used to control both burners. is accomplished by thermocouples 37 and 38 connected with temperature controller 39 which regulates the flow of fuel gas to both of the radiant burners. Thermocouple 37 can be omitted and the process controlled by thermocouple 38 alone. Both thermocouples can be used and separate controllers provided to control the separate burners independently.. The number of burners either within or without the dryer can be larger or smaller than the number illustrated.

Although the radiant burners are very efiicient, both from the standpoint of conversion of fuel into heat and from the standpoint of transfer of heat to the material being dried, with some particulate materials, especially as they approach dryness, some difliculty with overheating and possible ignition may occur by direct exposure to the radiant flame. In the embodiment of FIGURE 1 this is avoided by utilizing indirect heat exchange in the later drying stages within the dryer drum, utilizing in this embodiment burners 41 and 42 support outside drum 11, adjacent thereto. Fuel is supplied to these burners through a pipe 43, control for the individual burners being by means of motor valves 44 and 45 responsive to temperature controller 46 in response to the temperature measured by thermocouple 47 in discharge pipe 18.

Normally, cooling air is admitted through inlet 51 and valve 52 only when it is desired to cool drum 11, as for example for repair, cleanup, etc. However, if it is desired to control the temperature of the purge gas leaving through pipe 53, a temperature controller 54 is employed to actuate valve 52.

In FIGURE 2, drum 61 is supported on rollers 62 and 63. Drum 61 is rotated by supplying motive power to one or more of the supporting rollers, as for example an electric motor 64. Inlet hood 66, discharge hood 67 and support truss 68 are fastened together-as a unitary structure and supported by rollers 71 and 72 on columns 73 and 74, respectively.

Inlet hood 66 comprises a cylindrical member 76 and provides a rotary seal with the inlet end of drum 61 by means of a packing 77. Extending through member 76 are four pipes 78, 79, 80 and 81 for conducting a combustible mixture to the radiant burners within drum -61.

Attached to a plate 82 on the inside end of member 76 are four pipes 83, 84, 85, and 86 which are the main members of the support truss 68 which extends throughout the length of drum 61,'and also communicate with pipes '78, 79, 80, and 81 to carry the combustible mixture to the burner.

Discharge hood 67 comprisesan inner cylindrical member 91 which is connected by means of a plate 92 with the pipes 83, S4, 85 and 86 of truss 68. The discharge end of drum 61 is provided with an outer cylindrical member 93 which is provided with a seal in cooperation with discharge hood 6'7.

Inlet hood 66 is provided with a pipe connection 96 for the removal of hot combustion products from the interior of drum 61 while discharge hood 67 is provided with a pipe connection 97 for cooling air inlet. A butterfly valve Inlet pipe 95 extends through inlet hood 66 into drum 61.

A pipe 101 communicates with pipe connection 96 and with the inlet of a compressor 1G2 to remove the hot prodnets of combustion through pipe 103 to the separation means 164. Compressor 162' can be any suitable type of gas compressor or fan which will move the desired quantity of hot combustion products with the necessary pressure through the separation means 104. In the embodiment illustrated, separation means 16 is shown schematically as a cyclone separator. The selection of the This.

little loss in temperature as possible.

separation means involves a compromise between very efficient separation, as for example by bag filter means, and the desire to transmit the products so that there is as It is desirable to remove as much of the suspended solids as possible to prevent deposition of the solids on the outside of drum 61 and the resulting reduction in heat transfer rate. On the other hand, to use an extremely eflicient separation means such as a bag filter requires the reduction of temperature which may offset the extra filtration efliciency accomplished. separation, such as a multiple unit cyclone, is a useful separation means. With such a separation means the high temperature of the gases can be preserved and enough of the solid particles removed to prevent undue deposition on the outside of drum 61. On the other hand, if less efiicient separation means are used, it is possible to provide scrapers on the outside of drums 61 to prevent excessive accumulation of solid material.

The relatively clean hot combustion products are then transported through. pipe 166 through the interior of a shroud 107 extending around drum 61. The gases pass around drum 61 imparting additional heat to the drum and thus to the material being dried therein and are discharged through a stack 168. Normally the gas from stack 16:? is passed to a bag filter installation. Therefore, a temperature control is provided for this stream by' utilizing a temperature sensing element 111, a temperature controller 112 and a motor valve 113 in a pipe 114 which permits cooling air to pass into stack ltlswhen the temperature rises above a desired amount.

Four banks of radiant burners 116, 117, 118, and 119 are supported from truss 68, each bank comprising a plurality of individual radiant burners. Suitable burners for this type of installation include among others burners which comprise ceramic cups on which the burner flames are impinged and which cups become incandescent and thus transmit radiant heat, and burners which comprise porous ceramic masses through which the combustible mixture passes and whereon the combustible mixture is burned, and porous metal radiating screens in front of the ceramic bodies which metal screens transmit a substantial portion of the radiant energy. However, other types of radiant burners in which a combustible mixture is burned and the resulting flame impinged on a refractory material to supply radiant heat can be utilized. Although generally the refractory on which the flame impinges is in the nature of a ceramic material, it is possible also to generate radiant heat by impinging a flame upon a refractory metal, that is a metal which is difi'icult to fuse or melt, which will withstand the high temperature involved.

Therefore, in this application the expression refractory material is used in the broad sense to include those materials upon which a flame can be impinged to produce radiant heat without quickly destroying the material itself.

A combustible mixture is formed by mixing air and natural gas in the proportions desired by means of combustion controller 121. This can be, for example, a Selas combustion controller type L, which supplies the combustible mixture of the desired proportions and at the desired pressure. The combustible mixture is supplied to each of the burner banks separately through pipes 122, 123, 124, and 125, controlled by motor valves 126, 127, 128 and 129, respectively. Thermocouples 131, 132, 133 and 134 are provided to measure the temperature of the added particulate material as it leaves each of the banks of burners. Each of these thermocouples is connected with a controller 136, 137, 138 and 139, respectively, to regulate the flow of combustible mixture to the burner banks 116, 117, 118 and 119, respectively.

The embodiment illustrated in FIGURE 2 is particularly well suited, as is the embodiment of FIGURE 1, to the drying of wet pelleted carbon black. The pellets from the wet pelleting step contain about 45 to 55 Weight percent of Water and generally very close to 50 percent.

It has been found that some form of cyclone In the dryer the moisture content is reduced to less than 1.0 percent, generally between about 0.3 to 0.5 Weight percent.

Example In an example of the operation of my invention as' tween 0.3 and 0.5 percent. The temperature of the enter ing pellets is 170 F. With the radiant burners burning 6 Although it has been suggested that utilizing the very hot radiant burner inside a rotary drum wherein carbon black is being dried would raise a problem of fire hazard or adversely affect the properties of the carbon black, this has not proved to be the case. In a test drum, 23 inches in diameter and 35 inches in length and rotating to give a peripheral speed of 63 ft. per minute, the feed Was stopped and the black circulated under a 1550 F. burner for 30 minutes. The temperature of the carbon black bed stabilized at 1200 F. after about 1 5 minutes and the black did not ignite.

Table I shows sample drying runs and Table II shows carbon black properties and rubber reinforcing characteristics.

10,000 cubic feet of gas per hour, a gas consisting of 85 15 percent CH and 15 percent C H with zero excess air, TA LE I the burners have a surface temperature of 2040 F. and the gas discharged through pipe 96 is at a temperature of S 1 Jg Fitnal bed q E zal i gle 750 F. This gas is passed through blower 102 and cy- 2 amlie $9 5,35 ,fif f tgj clone separator 104 at a rate of 3819 cubic feet per minute and passed into hood 107 in indirect heat exchange 1 1,400 650 4&7 0 with the carbon black in drum 61 at a temperature of g Egg 338 Egg 3 is 700 F. The temperature of the gas leaving hood 107 112 1:550 150 3 30 is 645 F. Cooling an is supplied through valve 114 at 2 5 0Ve11df1ed-O0I1tr01 a rate of 3060 cubic ft. per minute at 100 F., thus re- TABLE 11 Sample No. 1 2 3 4 5 IRB #1 IRB #1 IRB #1 Minutes cure- Modulus: v

1,520 1,580 1,070/1,530 1,550 1,530 1, 340 1,780 1,850 1,900 1,990 2,050/2,050 1,900 1,900 2,130 2,150 2,140 Tensile:

15 3,200 3,200 3,550/3,000 3,550 3,130 3,420 3,470 3, 000 30 3,300 3,350 3,070/3,030 3,750 3,470 3,720 3,700 3,700 Elongation:

15 430 500 500/530 520 500 480 490 480 30 470 490 470/470 500 400 470 450 470 Shore A:

15 59 59 00/53 '59 00 00 59 57 30 02 02 02/02 03 04 02 02 02 Pack point 70 94 80 120 Pellet distribution (percent) on each screen Screen mesh:

' 1 2 3 Use to show which samples were tested at the same time.

ducing the outlet temperature of the gas to the bag filters (not shown) to 475 F. The total gas discharged at this temperature is 5750 cubic ft. per minute. Satisfactory transfer of heat from the burners to the'bed of carbon black pellets is obtained when the burners are placed 12 inches above the bed height with the drum rotating.

Although I have illustrated my invention having radi-,

ant burners, in the embodiment of FIGURE 2 and the embodiment of FIGURE 3 one or more of the heaters toward the discharge end of the dryer drum can be electrical In this manner, the relative ease of control of.

heaters. electrical units can be utilized while still taking advantage of the high heat release and economy of the radiant burners. Suitable electrical controllers, for example rheostats, can be used in place of the motor valves used with the burners.

Although my invention has been described using thermocouples to measure the bed temperature, other suitable temperature sensing devices, for example radiation pyrometers, can be used.

- dryer as measured by a temperature sensitive element such as thermocouple 153. The temperature sensitive element can be placed in the stream being discharged from the dryer or can be placed inside the dryer at a location near the discharge outlet to measure the temperature of particulate material in condition for discharge from the dryer. In the embodiment illustrated, controller 152 is a pneumatic instrument and supplies air pressure to the' diaphragms of motor valves 147-150. Under certain cond-itions suitable control can be obtained either by actuating all of the valves simultaneously or, through the use of suitable spring forces, the valves can be made to operate sequentially. For example, it may be desirable to have valve 150 begin to operate with the first output signal from controller 152 and to be in its fully actuated position by the time the pressure output from controller 152 reaches 3 pounds, to have valve 149 operate between 3 and 6 pounds, valve 148 bet-ween 6 and 9 pounds and valve 147 between 9 and 12 pounds. With this type of operation, when the discharge temperature begins to exceed the desirable temperature, burner 144 is cut down either substantially off or to an intermediate position depending upon the setting of valve 150. That is, valve 150 can be made to close substantially or to close merely to an intermediate position as a limit. Similarly, valves 147, 148,1and 149 can be made to operate in this manner. If the temperature continues to rise, the output from controller 152 continues to rise and reaches the range at which valve 149 is operative and so on, gradually cutting the burners back from the discharge end toward the inlet end.

This type of control system also is applicable to actuation of all valves at the same pressure, in whichv instance all of the burners are cut back simultaneously to maintain the desired discharge temperature. In the operation of the control system illustrated in FIGURE 2, each of the controllers 136139 preferably is set for the same temperature. Where a stream of particulate material is being dried, for example, where the stream is a stream of wet carbon black pellets, the temperature of the bed tends to reach an intermediate maximum temperature relatively quickly, the temperature being determined by the boiling temperature of the liquid being removed. For example, when pellets containing excess water are being dried, the temperature of the bed reaches about 205 to 220 F. under atmospheric pressure. This temperature remains constant until the particles approach dryness at which time the temperature tends to rise rapidly. Therefore, with all of the burners 116, 117, and 118 operating to capacity, burner 119 supplies suflicient heat to complete the drying operation, under normal conditions, under the influence of a temperature measured by thermocouple 134. If the water content of the particles or the flow rate decreases sufficiently that the particles become dry prior to falling under the influence of burner 119, thermocouple 133 indicates a rise, and control of the operation then is under the influence of burner 118, and so on back toward the inlet of the dryer. For example, when carbon black pellets are being dried, it is found that an outlet temperature of approximately 350 F. is desirable. With all of the controllers 136-139 set to control at 350 F., it is seen that under normal conditions, when the black approaches 350 only under-the influence of burner 119, this latter burner is doing the controlling, burners 116- 118 being operated at maximum capacity. On the other hand, if the demands on the dryer decreases the temperature of 133 begins to rise, and when it reaches 350 F. burner 118 comes under the control of controller 138.

The process steps and apparatus including control method and apparatus are applicable to the chemical treatment of carbon black at elevated temperatures. Such treatment includes, for example, the maintenance of surface temperatures on the carbon black in the range of 400 to 1000 F., preferably 650 to 850 F. while contacting the black. with an oxidizing atmosphere in which the partial pressure of oxygen is in the range of 8 to 80 mm. Hg. My invention also is applicable to treatment with other materials such as oxyhalides as disclosed in U.S. 2,641,533 (1953), S as disclosed in U.S. 2,636,831 (1953), etc.

Suitable radiant burners for use in my invention include, for example, burners comprising a ceramic cup and a burner which impinges a flame on the cup thus causing the ceramic material to glow and transmit radiant energy and burners having a block of porous ceramic material on which combustion takes place to cause incandescence of the ceramic mass. Either type of burner can be supplied with a metal screen or grid in front of the ceramic mass to cause a substantial amount of the radiant heat to be propagated from the metal surface. In this application, the word refractory" has been used in its broad sense to include materials which are diflicult to fuse or melt, and thus includes refractory metals and metallic compositions and cement as well as ceramic materials. Cermet is used to mean a fired mixture of ceramic material and finely divided metal.

When my invention is used for drying ammonium nitrate prills the temperature is maintained within the range of to F., preferably in the range of 148 to 157 F. When my invention is utilized in drying wet carbon black pellets each of the heating zones is controlled to maintain a temperature in the range of 200 to 1000 F., that is each zone is controlled to a selected temperature within this range. Ordinarily, the maximum temperature of carbon black being dried is no higher than 500 F., preferably about 350 F.

The control of the temperature of ammonium nitrate prills while drying is to prevent crystalline phase changes. To prevent overheating the surface it is important that the prills be in a thin layer or in constant motion to expose different surfaces and different prills to the heat source. This is accomplished advantageously in a tumbling type dryer such as a rotary dryer as disclosed herein.

It is also important at the low drying temperature to provide a low humidity atmosphere to remove the expelled water. Thus in effect, the best dryer combines the use of radiant heat to heat the water internally within theprills, with the low humidity atmosphere of a con vective dryer. To maintain a low humidity it is desirable to remove the products of combustion.

As pointed out earlier, radiant heat is generated by a burning gas either by impinging a pre-existing flame on a mass of refractory material, or by causing combustion to occur on the surface of the refractory. In either case, a refractory mass is heated by burning a combustible gas. Thegas can be premixed with air or other preoxygen contaming gas, or can contact it at the instant of combustion.

The filter to which the gas from stack 108 is passed can be an installation made especially for that purpose or, since the radiant burners can be operated efficiently with little or no excess air, this gas can be taken to a filter installation for the eflluent from a furnace used to produce carbon black. The gas can be combined with the furnace eflluent prior to entry into the filter or can be brought into the filter through a separate inlet. Preferably the filter is a bag filter installation.

I can also utilize radiant burners to advantage in removing volatile liquid from particulate material by placing the burners outside a rotating dryer drum. Burners 42 in FIGURE 1 can be radiant burners.

A complete drying operation can be accomplished by one or more radiant burners positioned to direct heat on the outside of a dryer drum. Very eflicient utilization of heat and good drying capacity are obtained. In a desirable installation, at least a portion of the products of combustion are passed through the drum to further utilize the heat and to purge the drum of accumulating vapors, and these products can then be passed to a separate filter or to the filter used for the efliuent from a carbon black making furnace, preferably a bag filter.

Reasonable variation and modification are possible within the scope of my invention which sets forth method and apparatus for drying particulate material utilizing rotary drying means and in which a portion of the heat for drying is supplied by direct radiation from radiant burners within the dryer drum and the remainder of the heat is supplied by indirect heat exchange with the burners adjacent the drum, and means and apparatus for rotary drum drying utilizing radiant burners inside the dryer and passing the hot products of combustion in indirect heat exchange with the material to be dried by passing the gases around the dryer drum, and the application of the process and apparatus to the treating of carbon black at elevated temperatures.

I claim: 1. A process for removing volatile liquid from particulate material, comprising:

passing said particulate material through a drying zone; rotating said drying zone to maintain an agitated bed therein; generating radiant heat by burning directly in said zone a combustible mixture in a radiant burner solely within a first portion of said drying zone and impinging the resulting fiame on a mass of refractory material of said burner to make said refractory material incandescent thus heating said particulate material in said first portion of said drying zone by subjecting said bed directly to said radiant heat to remove'a portion of said volatile liquid; and generating heat by burning a combustible mixture solely outside but adjacent a second portion of said drying zone said second portion being in direct open communication with said first portion in longitudinal relation thus heating said particulate material in said second portion of said drying zone by subjecting said bed indirectly to said heat to remove an additional amount of said volatile liquid. 2. A process for operating a rotary dryer, comprising; passing particulate material containing a volatile liquid through said dryer; rotating said dryer to maintain an agitated bed therein; generating radiant heat by supplying a combustible mixture to and burning in a radiant burner Within a first portion of said dryer and impinging the resulting flame on a mass of refractory material of said burner to make said refractory material incandescent thus heating said particulate material in said first portion of said dryer by subjecting said bed directly to said radiant heat to remove a portion of said volatile liquid; generating heat by supplying and burning a combustible mixture outside but adjacent a second portion of said dryer thus heating said particulate material in said second portion of said dryer by subjecting said bed indirectly to said heat to remove an additional amount of said volatile liquid; measuring the temperature of said bed in said first portion of said dryer; controlling the supply ofcombustible mixture in said first portion of said dryer responsive to the measured temperature of said bed; measuring the temperature of the particulate material discharged from said dryer; and controlling the supply of combustible mixture burned outside said second portion of said dryer responsive to the measured temperature of said discharge material. 3. A process for operating a rotary dryer, comprising: passing carbon black pellets containing excess moisture through said dryer; rotating said dryer to maintain said pellets in an agitated bed therein; generating radiant heat by supplying a combustible mixture to and burning in a radiant burner within a first portion of said dryer and impinging the resulting flame on a mass of refractory material of said burner to make said refractory material incandescent thus heating said pellets in said first portion of said dryer by subjecting said bed directly to said radiant heat to remove a portion of said moisture; generating heat by supplying and burning a combustible mixture outside but adjacent a second portion of said dryer thus heating said pellets in said second portion of said dryer by subjecting said bed indirectly to said heat to remove an additional amount of said moisture;

measuring the temperature of said bed in said first portion of said dryer;

controlling the supply of combustible mixture burned in said first portion of said dryer responsive to the measured temperature of said bed to prevent overheating ,said bed;

measuring the temperature of the particulate material discharged from said heating zone; and

controlling the supply of combustible mixtureburned outside said second portion of said heating zone responsive to the measured temperature of said discharged material tomaintain said temperature of said discharged material in the range of 250-550 F.

4. A process for operating a rotary dryer, comprising:

passing particulate material containing a volatile liquid through said dryer;

rotating said dryer to maintain an agitated bed therein;

generating radiant heat by burning directly in said zone a combustible mixture in a radiant burner solely wtihin a first portion of said dryer and impinging the resulting flame on a mass of refractory material of said burner to make said refractory material incandescent thus heating said particulate material in said first portion of said dryer by subjecting said bed directly to said radiant heat to remove a portion of said volatile liquid; and

generating radiant heat by burning a combustible mixture solely outside but adjacent a second portion of said dryer, said second portion being in direct open communication with said first portion in longitudinal relation and impinging the resulting flame on a mass of refractory material to make said refractory material incandescent thus heating said particulate material in said second portion of said dryer by subjecting said bed indirectly to said radiant heat to remove an additional amount of said volatile liquid.

5. A process for operating a rotary dryer, comprising:

passing particulate material containing a volatile liquid through said dryer;

rotating said dryer to maintain an agitated bed therein;

generating radiant heat by supplying a combustible mixture to and burning in a radiant burner a first portion of said dryer and impinging the resulting flame on a mass of refractory material of said vburner to make said refractory material incandescent thus heating said particulate material in said first portion of said dryer by subjecting said bed directly to said radiant heat to remove a portion of said volatile liquid; I

generating radiant heat by supplying and burning a combustible mixture within a second portion of said dryer and impinging the resulting flame on a mass of refractory material to make said refractory material incandescent thus heating said particulate material in a second portion of said dryer by subjecting said bed directly to said radiant heat to remove a second portion of said volatile liquid;

generating heat by burning a combustible mixture outside but adjacent a third portion of said dryer thus heating said particulate material in said third portion of said dryer by subjecting said bed indirectly to said heat to remove an additional amount of said volatile liquid;

measuring the temperature of said bed in said first portion of 'said dryer; t

controlling the supply of combustible mixture burned in said first portion of said heating zone responsive to the measured temperature in said firstportion;

measuring the temperature of said bed in said second portion of said dryer;

controlling the supply of combustible mixture burned in said second portion of said dryer responsive to the measured temperature of said second portion;

measuring the temperature of the particulate material discharged from said heating zone; and

controlling the supply of combustible mixture burned outside said third port-ion of said heating zone responsive to the measured temperature of said discharged material.

6. A process for operating a rotary dryer, comprising:

passing particulate material containing a volatile liquid through said dryer;

rotating said dryer to maintain an agitated bed therein;

generating radiant heat by supplying a combustible mixture to and burning in a radiant burner within a first portion of said dryer and impinging the resulting flame on a mass of refractory material of said burner to make said refractory material incandescent thus heating said particulate material in said first portion of said dryer by subjecting said bed directly to said radiant heat to remove a portion of said volatile liquid;

generating radiant heat by supplying and burning a combustible mixture within a second portion of said dryer and impinging the resulting flame on a second mass of refractory material to make said second refractory material incandescent thus heating said particulate material in said second portion of said dryer by subjecting said bed directly to said radiant heat to remove a portion of said volatile liquid;

sensing a first temperature of said bed in said second portion and controlling the supply of combustible mixture to said second portion in response to said first measured temperature;

measuring a second temperature of said bed in said first portion and controlling the supply of combustible mixture to said first portion in response to said second measured temperature; and

selecting the control temperature in said first zone and said second zone at identical values.

7. A process for chemical treatment of particulate carbon black, which comprises:

passing said carbon black through a treating zone;

maintaining said carbon black in an agitated bed in said treating zone;

generating radiant heat solely in a first portion of said treating zone by heating a mass of refractory material of a radiant burner to incandescence by burning directly in said zone a combustible mixture thus heating said carbon black in said first portion of said treating zone by subjecting said bed directly to said radiant heat;

generating heat by burning a combustible mixture solely outside but adjacent a second portion of said treating zone, said second portion being in direct open communication with said first portion in longitudinal relation thus, heating said carbon black in said second portion of said treating zone by subjecting said bed indirectly to said heat; and

contacting said carbon black in said treating zone with a chemical treating agent effective to obtain said chemical treatment.

8. A dryer for removing volatile liquid from particulate material, comprising:

a rotary drum;

means to feed said particulate material into said drum;

means to rotate said drum at a controlled speed to move said material through said drum to maintain said material in an agitated bed;

means to generate radiant heat solely in a first portion of said drum, comprising a first radiant burner comprising a first mass of refractory material, means to supply a combustible mixture to said first burner to produce a flame and impinge said flame on said first mass to make said refractory material incandescent;

means to support said first mass in said drum to supply radiant heat directly to said bed in said first portion of said drum to remove a portion of said volatile liquid;

means to generate radiant heat solely outside but adja cent a second portion of said drum, comprising a second radiant burner comprising a second mass of refractory material, means to supply a combustible mixture to said second burner to produce a flame and impinge said flame on said second mass to make said refractory material incandescent, said second portion being in direct open communication with said first portion in longitudinal relation; and

means to support said second mass outside said drum to heat said particulate material in said second portion in said drum to supply heat indirectly to said particulate material to remove an additional amount of volatile liquid.

9. A dryer for removing volatile liquid from particulate material, comprising:

a rotary drum; means to feed said particulate material into said drum; means to rotate said drum at a controlled speed to move said material through said drum to maintain said material in an agitated bed; means to generate radiant heat in a first portion of said drum, comprising a first radiant burner comprising a first mass of refractory material, means to supply a combustible mixture to said first burner to produce a flame and impinge said flame on said first mass to make said refractory material incandescent; means to support said first mass in said drum to supply radiant heat directly to said bed in said first portion in said first drum to remove a portion of said volatile liquid; means to generate heat outside but adjacent a second portion of said drum, comprising a second burner and means :to supply combustible mixture to said second burner to produce a flame, said second portion being in direct open communication with said first portion in longitudinal relation; means to support said second burner outside said drum to heat said particulate material in said second portion of said drum indirectly to remove an additional amount of said volatile liquid; means to measure the temperature of said bed in a first portion of said drum; means to control the supply of combustible mixture to said first burner responsive to the measured temperature of said bed; means to measure the temperature of the particulate material discharged from said drum; and means to control the supply of combustible mixture to said second burner responsive to the measured temperature of said discharged material. It A dryer for removing volatile liquid from particulate material, comprising:

a rotary drum;

means to feed said particulate material into said drum;

means to rotate said drum at a controlled speed to move said material through said drum to maintain said material in an agitated bed;

means to generate radiant heat in a first portion of said drum, comprising a first radian-t burner comprising a first mass of refractory material, means to supply a combustible mixture to said first burner to produce a flame and impinge said flame on said first mass to make said refractory material incandescent;

means to support said first mass in said drum to supply radiant heat directly to said bed in said first portion of said drum to remove a portion of said volatile liquid;

means to generate radiant heat in a second portion of said drum, comprising a second radiant burner comprising a first mass of refractory material, means to supply combustible mixture to said second burner to produce a flame and impinge said flame on said second mass to make said refractory material incandescent, said second portion being in direct open communication With said first portion in longitudinal relation;

means to support said second mass in said drum to supply radiant heat directly to said bed in said second portion of said dun-m to remove an additional amount of said volatile liquid;

means to measure the temperature of said bed in said first portion of said drum;

means to control the supply of combustible mixture to said first burner responsive to the measured temperature of said bed in said first portion;

means to measure .the temperature of said bed in said second portion of said drum; and

means to control the supply of combustible mixture to said second burner responsive to the measured temperature of said bed in said second portion.

References Cited by the Examiner UNITED STATES PATENTS Davis -a 239259.7

Thayer 236-33 X W'hitmore 34137 Johnson et a1 26333 X Barnes 263 33 Blaha 158113 Campbell 158-113 King 34135 Loewen 34-135 X WILLIAM F ODEA, Primary Examiner. NORMAN YUDKOFF, Examiner. 

1. A PROCESS FOR REMOVING VOLATILE LIQUID FROM PARTICULATE MATERIAL, COMPRISING: PASSING SAID PARTICULATE MATERIAL THROUGH A DRYING ZONE; ROTATING SAID DRYING ZONE TO MAINTAIN AN AGITATED BED THEREIN; GENERATING RADICAN HEAT BY BURNING DIRECTLY IN SAID ZONE A COMBUSTIBLE MIXTURE IN A RADIANT BURNER SOLELY WITHIN A FIRST PORTION OF SAID DRYING ZONE AND IMPINGING THE RESULTING FLAME ON A MASS OF REFRACTORY MATERIAL OF SAID BURNER TO MAKE SAID REFRACTORY MATERIAL INCANDESCENT THUS HEATING SAID PARTICULATE MATERIAL IN SAID FIRST PORTION OF SAID DRYING ZONE BY SUBJECTING SAID BED DIRECTLY TO SAID RADICANT HEAT TO REMOVE A PORTION OF SAID VOLATILE LIQUID; AND GENERATING HEAT BY BURNING A COMBUSTIBLE MIXTURE SOLELY OUTSIDE BUT ADJACENT A SECOND PORTION OF SAID DRYING ZONE SAID SECOND PORTION BEING IN DIRECT OPEN COMMUNICATION WITH SAID FIRST PORTION IN LONGITUDINAL RELATION THUS HEATING SAID PARTICULATE MATERIAL IN SAID SECOND PORTION OF SAID DRYING ZONE BY SUBJECTING SAID BED INDIRECTLY TO SAID HEAT TO REMOVE AN ADDITIONAL AMOUNT OF SAID VOLATILE LIQUID. 